According to This website the .VCD extension indicates a Windows video disk image format (presumably similar to the Mac .dmg format), so you would need an application that can extract the disk image(s). The .DAT extensions apparently indicate the data stream of the videos. The same website suggests a freeware program for Mac OSX called "VCDGear" to open the .DAT files. You can download the VCDGear program from versiontracker. According to the versiontracker description, it appears to be a command-line application, but the user reviews are positive (OS requirements list 10.4 as the highest OSX version; dunno if it will run on 10.5). The file is only 154 KB, so probably worth a try.